My 2012 eco mt car has been to the dealership twice for a "service stabilitrack" message on the center screen. They replaced the ground wire on the first trip that did not fix the problem. Now I am getting the same message with a random mis-fire code and they are telling me that the spark plugs are the reason, and they want to do a full injector cleaning ($300 for both) but there are no codes for the injectors. Are they just guessing now?